Heretofore, lamination type three-dimensional object forming methods (hereinafter referred to as “laminate forming method(s)”), such as stereolithography, have been actively used in many fields. The methods described above are each a method for forming an arbitrary three-dimensional object by sequentially laminating cross-sectional patterns thereof. In those methods, a three-dimensional object can be directly formed from a three-dimensional (design) data without using a mold or the like. Hence, those methods have been frequently used, for example, for prototype production in which a small number of three-dimensional objects are highly required to be prepared in a short period of time.
As characteristic restriction of the laminate forming method, for example, an indispensable support may be mentioned. In the laminate forming method, since layer-shaped patterns are laminated to each other, for example, an object having an isolated portion, such as a front end of a hanging tree branch, in the course of manufacturing cannot be manufactured in principle. In order to form the portion as described above by the laminate forming method, it is necessary that a support, which is not necessary in a final state, be formed under the isolated portion and then removed by some type of method after the object is formed.
The removal of the support is basically carried out by person's hand working. In the laminate forming method, in general, instead of forming a large number of the same object, objects having different shapes are manufactured in many cases in accordance with requirements from users. Hence, it has been very difficult to automatically remove supports from the objects having different shapes as described above.
In order to reduce the support removing burden, a method has been known in which the support is formed from a material different from a model forming material which forms the object. According to this method, when a melting agent which melts a support material but not the model forming material is used, the support can be easily removed. In addition, even when a material which is not melted but is easily removed is used, the support removing burden can be significantly reduced.
In the laminate forming method, in order to realize object formation with an excellent accuracy, the thickness of each layer to be laminated is also required to have a sufficient accuracy. In order to preferentially realize easy removal of the support, when the support is formed from a material different from the model forming material, patterns formed from two types of materials are necessarily aligned with each other with a high accuracy. When the patterns are not well aligned with each other, a gap is formed therebetween, and an overhanging portion may not be supported. In addition, when the model forming material and the support material are overlapped with each other, a protrusion may be formed, or adhesion of the surface of the model forming material may be degraded, so that the strength of the three-dimensional object may be decreased in some cases. In addition, when layers having a uniform thickness are formed from different materials, in view of the accuracy necessary for material supply and the change in volume caused by environmental influences, significantly tight control is required.
United States Patent Application No. 2001/0042598 has disclosed a method in which after a layer having a shape of a part of a final three-dimensional object is formed, a material to be used as a support is provided so as to surround this layer, and the upper surface of the support is then ground to have a design thickness. According to the method described above, subsequently, a material which forms the three-dimensional object is further laminated on the support and the layer which forms an in-process three-dimensional object.
However, according to the method described above, if a removed material which is ground off again adheres to the object, the quality of the three-dimensional object to be manufactured may not be sufficiently satisfied in some cases. In addition, the case in which a fine model forming portion cannot be formed to have a desired shape due to heat and/or a mechanical stress generated during grinding may occur in some cases. Furthermore, in order to perform highly accurate grinding, a very long processing time is required.